[unreadable] Atrial fibrillation (AF) is the most common cardiac dysarrhythmia, currently affecting over 2 million Americans. Embolic material from thrombus in the fibrillating left atrium (LA) has been documented as a major cause of stroke, especially in the elderly. Over 90 percent of LA thrombus lies within the left atrial appendage (LAA). It has been estimated that 20 % of stroke victims were afflicted with AF and the American Heart Association has recently estimated that the overall cost associated with stroke exceeds $43 billion per year. Currently, the most widely used therapy for patients with AF is oral warfarin to increase blood clotting times. However it has been reported that while warfarin can significantly reduce risk, it remains both underutilized (only 34.7% of eligible patients in one study) and misutilized (over 50% of patients with clotting times out of range in another study). Recently, isolation of the LAA has surfaced as a possible preventive therapy for AF related stroke. Ension has begun development of a device ultimately intended to manipulate the LAA and functionally isolate it from the circulation. This device would be compact enough to use endoscopically as a standalone procedure, but could also be used during open-heart operations where isolation of the LAA would be part of the overall operation. Development is proceeding in three phases. Current device iterations only have the capability to grasp the LAA and are too large for endoscopic use. In this Phase I proposal we intend to decrease device size, improve its capabilities and flexibility, and perform both acute and chronic in vivo experiments in pigs to show the effects of LAA functional isolation. Among our specific aims in Phase II would be the incorporation of a stapling component so that only one tool would be required to grasp, manipulate, and functionally isolate the LAA. [unreadable] [unreadable]